Formation of the placenta is a crucial step in mammalian pregnancy. Apart from its function
in ensuring an optimal supply of nutrients and oxygen to the fetus, the placenta is also the
interface at which allo-recognition of invading trophoblast cells by the maternal immune
system can potentially occur. We summarise here the “state of the art” on how variability of
immune system genes that code for major histocompatibility complex (MHC) molecules and
natural killer receptors (NKR) may impact on human placentation. MHC and NKR are the …